Such input circuits are known and by now have many measuring transducers and actuators which are connected, via a 4-20 mA interface, to analog detection and output assemblies via an integrated HART interface. This results in the need to both digitize the actual measured value, which is transmitted by means of the 4-20 mA current, using analog/digital conversion and to demodulate the HART signal modulated onto this current and to receive the message transmitted thereby.
The illustration in FIG. 1 shows such an input circuit.
It can be seen that such a known input circuit is comparatively complicated since it comprises an analog/digital converter, a bandpass filter and a HART demodulator.